Compact Collinear Quasi-Yagi Antenna Array for Wireless Energy Harvesting

Abstract

A novel quasi-Yagi antenna array with a thin configuration is proposed in this work. Different from traditional high-gain Yagi or quasi-Yagi antennas, which need large widths to hold either several parasitic elements along the radiation direction or extra feeding networks like baluns and power dividers, this design adopts a collinear antenna as the driven part and employs a few collinear parasitic strips. Thus, a high gain can be realized with a narrow width. Based on the analysis of the collinear antenna, effect of parasitic strips and impedance matching, a compact antenna prototype with a size of 26 $\text {mm}\times 190.5$ mm is proposed and fabricated. The measured results show that the realized gain is 8-8.7 dBi from 2.3 to 2.63 GHz. With a rectifying circuit, maximum dc power of 1- $39.2~\mu \text{W}$ can be produced under a power density of 0.05-1 $\mu \text{W}$ /cm2 at 2.45 GHz, while more than $31~\mu \text{W}$ obtained in an azimuth angle range of 100° for a power density of ~\mu \text{W}$ /cm2. To further validate the compactness, an angle-diversity prototype consisting of two back-to-back proposed array antennas is also presented. It nearly doubles the harvesting coverage with a size less than that of two antennas.